Operational experience with the readout system of the MINOS vertex tracker

The MINOS vertex tracker is a compact instrument built for in-beam spectroscopy of exotic nuclei. Its main component is a ~30 cm long hollow cylinder shape time projection chamber (TPC) surrounding a liquid hydrogen target. The anode of the TPC is read out by a Micromegas detector segmented in 18 concentric rings of 2 mm × 2 mm pads totaling 3604 channels. A dedicated system based on the AFTER and AGET chips was designed to read out this TPC, and the required software to configure, monitor and acquire data was developed. After a construction period of two years and the validation of the instrument in a test beam, four nuclear physics experiments exploiting MINOS have been successfully conducted at RIKEN, Japan. We describe the prominent aspects of the readout system of MINOS and we report on lessons learned during the three years of exploitation.